Structure of a CGI-58 motif provides the molecular basis of lipid droplet anchoring.

Triacylglycerols (TGs) stored in lipid droplets (LDs) are hydrolyzed in a highly regulated metabolic process called lipolysis to free fatty acids that serve as energy substrates for ß-oxidation, precursors for membrane lipids and signaling molecules. Comparative gene identification-58 (CGI-58) stimulates the enzymatic activity of adipose triglyceride lipase (ATGL), which catalyzes the hydrolysis of TGs to diacylglycerols and free fatty acids. In adipose tissue, protein-protein interactions between CGI-58 and the LD coating protein perilipin 1 restrain the ability of CGI-58 to activate ATGL under basal conditions. Phosphorylation of perilipin 1 disrupts these interactions and mobilizes CGI-58 for the activation of ATGL. We have previously demonstrated that the removal of a peptide at the N terminus (residues 10-31) of CGI-58 abrogates CGI-58 localization to LDs and CGI-58-mediated activation of ATGL. Here, we show that this tryptophan-rich N-terminal peptide serves as an independent LD anchor, with its three tryptophans serving as focal points of the left (harboring Trp(21) and Trp(25)) and right (harboring Trp(29)) anchor arms. The solution state NMR structure of a peptide comprising the LD anchor bound to dodecylphosphocholine micelles as LD mimic reveals that the left arm forms a concise hydrophobic core comprising tryptophans Trp(21) and Trp(25) and two adjacent leucines. Trp(29) serves as the core of a functionally independent anchor arm. Consequently, simultaneous tryptophan alanine permutations in both arms abolish localization and activity of CGI-58 as opposed to tryptophan substitutions that occur in only one arm.

A peptide derived from G0/G1 switch gene 2 acts as noncompetitive inhibitor of adipose triglyceride lipase.

The protein G0/G1 switch gene 2 (G0S2) is a small basic protein that functions as an endogenous inhibitor of adipose triglyceride lipase (ATGL), a key enzyme in intracellular lipolysis. In this study, we identified a short sequence covering residues Lys-20 to Ala-52 in G0S2 that is still fully capable of inhibiting mouse and human ATGL. We found that a synthetic peptide corresponding to this region inhibits ATGL in a noncompetitive manner in the nanomolar range. This peptide is highly selective for ATGL and does not inhibit other lipases, including hormone-sensitive lipase, monoacylglycerol lipase, lipoprotein lipase, and patatin domain-containing phospholipases 6 and 7. Because increased lipolysis is linked to the development of metabolic disorders, the inhibition of ATGL by G0S2-derived peptides may represent a novel therapeutic tool to modulate lipolysis.

Interaction study of pioglitazone with albumin by fluorescence spectroscopy and molecular docking.

Pioglitazone is a medicine of thiazolidinedione (TZD) class with hypoglycemic (antihyperglycemic, antidiabetic) action. Pioglitazone binding to human serum albumin (HSA) was investigated at different temperatures (290, 300 and 310 K) by fluorescence spectroscopic method. Molecular docking study was also carried out besides the experiments. Experimental results revealed that pioglitazone have an ability to quench the intrinsic fluorescence of HSA tryptophan through a static quenching procedure. The binding constant was determined using Stern-Volmer modified equation and energy transfer mechanisms of quenching were discussed. Thermodynamic parameters were also calculated according to enthalpy changes dependence on different temperatures. According to the theoretical and experimental results, hydrogen bonding was found to play a major role in the interaction of pioglitazone with HSA.